U.S. Pat. No. 4,189,527 discloses a cooling heat pipe which is orthogonal to a stack of plates within a metal-hydrogen cell. The heat pipe makes electrical contact with all plates having one of the polarities, whereas in the present invention, the cooling means, which may be a heat pipe, is electrically insulated from the electrochemical cells in the stack. The reference cooling scheme suffers from the drawback that there is a small area of contact between each plate and the heat pipe, causing very high temperatures in the vicinity of the heat pipe. Cooling fluid is not made to flow parallel to the planes of the plates as in the present invention.
U.S. Pat. No. 4,098,962 discloses a metal-hydrogen battery in which a cooling gas is made to flow orthogonal to the stacked cells, causing cell-to-cell temperature gradients. In the present invention, on the other hand, the cooling fluid flows parallel to the planes of the cells, resulting in temperature gradients within a cell, but not cell-to-cell.
U.S. Pat. No. 4,101,718 discloses a complex fuel cell in which three coolant channels 26 direct a fluid flow orthogonal to the planes of the individual cells.
The following U.S. patents disclose fuel cells in which coolant plates are sandwiched between the cells at infrequent intervals: U.S. Pat. Nos. 3,880,670; 4,192,906; 4,233,369; 4,310,605; 4,342,816; 4,397,918; 4,407,904; and 4,444,851. This technique suffers from several drawbacks: the cells remote from the coolant plates are not cooled to the same degree as cells proximate to the coolant plates, impairing the longevity of the stack; the individual coolant plates cannot be tested without taking the entire fuel cell structure apart; and the presence, in many cases, of gas pockets, worsens the thermal conductivity in the direction orthogonal to the planes of the cells. In a stack of bipolar cells, such a system would require the use a nonconductive cooling fluid to avoid short circuits between cells, since battery current flows through the cooling plates; in the present invention, on the other hand, the cooling fluid can be conductive or nonconductive.
U.S. Pat. No. 4,115,630 discloses a metal-hydrogen battery which does not have an active cooling system.